Laravel Datatable 与多个表的多对多关系答案

【问题标题】：Laravel Datatable ManyToMany relationship with multiple tablesLaravel Datatable 与多个表的多对多关系
【发布时间】：2019-10-16 19:19:51
【问题描述】：

Offer.php #model

use App\OfferCategory;
use App\OfferCountries;
use App\OfferCreative;
use App\OfferTools;
use App\OfferTraffic;

class Offer extends Model {
public function offer_countries() {
    return $this->belongsToMany(OfferCountries::class);
}

public function offer_categories() {
    return $this->belongsToMany(OfferCategory::class);
}

public function offer_creatives() {
    return $this->hasMany(OfferCreative::class);
}

public function offer_tools() {
    return $this->hasMany(OfferTools::class);
}

public function offer_traffic() {
    return $this->hasMany(OfferTraffic::class);
}

public function platforms() {
    return $this->hasMany(Platform::class);
}

}

OfferController.php

 public function getMediaData() {
//        $model = Offer::with('offer_traffic');
//        return DataTables::eloquent($model)
//                        ->addColumn('traffic', function (Offer $user) {
//                            return $user->offer_traffic->map(function($post) {
//                                        return str_limit($post->allowed_traffic, 30, '...');
//                                    })->implode('<br>');
//                        })
//                        ->toJson();

        return datatables(DB::table('offers'))->toJson();
    }

我想使用 offer.php 中给出的所有关系表和数据表中的图像。我已经尝试在控制器中使用注释代码，但无法获取请帮助我知道我做错了什么。

OfferCountries.php #model

使用应用\优惠；

class OfferCountries extends Model {

   function offers() {
         return $this->belongsToMany(Offer::class);
    }
}

【问题讨论】：

检查此文档...laravel.com/docs/5.8/…

标签： php mysql laravel laravel-5 datatable

【解决方案1】：

我会这样做，

在 Offer.php 中

 class Offer extends Model {
    public function offer_countries() {
        return $this->hasMany(OfferOfferCountries::class,'offer_id','id');
    }

    public function offer_categories() {
        return $this->hasMany(OfferOfferCategories::class,'offer_id','id');
    }

    public function offer_creatives() {
        return $this->hasMany(OfferCreative::class,'offer_id','id');
    }

    public function offer_tools() {
        return $this->hasMany(OfferTools::class,'offer_id','id');
    }

    public function offer_traffic() {
        return $this->hasMany(OfferTraffic::class,'offer_id','id');
    }

    public function platforms() {
        return $this->hasMany(Platform::class,'offer_id','id');
    }
  }

在 OfferOfferCountries.php 中

class OfferOfferCountries extends Model {
   public function countryDetail(){
     return $this->belongsTo(OfferCountries::class,'offercountry_id','id');
   }
}

在 OfferOfferCategory.php 中

class OfferOfferCategory extends Model {
   public function categoryDetail(){
     return $this->belongsTo(OfferCategory::class,'offercategory_id','id');
   }
}

现在在控制器中

public function getMediaData() {
        $data = Offer::with('offer_countries.countryDetail','offer_categories.categoryDetail','offer_creatives','offer_tools','offer_traffic','platforms')->get();

echo '<pre>';
print_r($data);

}

这应该为您提供所有对象的数组。您可以使用数据透视表，但我喜欢这种方式。

【讨论】：

谢谢你能帮忙处理数据表我收到错误允许的内存大小为 134217728 字节已用尽（试图分配 4096 字节）
好像代码某处有错误，很可能进入死循环。如果没有看到代码，就无法判断是什么导致了问题。如果这个答案解决了你的问题，你可以通过接受答案来结束这个问题

【解决方案2】：

我想 Laravel 不能自动处理你的关系，因为你的数据库中的关系字段不标准（offer_id 在很多情况下，而不是默认的主键）

要解决此问题，您必须手动提供必须在其之上构建关系的字段名称。

Offer.php

class Offer extends Model
{
    public function offer_countries()
    {
        // Here we provide parent key field name (offer_id) because we don't want to use the primary key for that
        return $this->belongsToMany(OfferCountries::class, null, null, null, 'offer_id');
    }

    public function offer_categories()
    {
        return $this->belongsToMany(OfferCategory::class, null, null, null, 'offer_id');
    }

    public function offer_tools()
    {
        // Map foreign key to local one 
        return $this->hasMany(OfferTools::class, 'offer_id', 'offer_id');
    }

    public function offer_traffic()
    {
        return $this->hasMany(OfferTraffic::class, 'offer_id', 'offer_id');
    }

    //...
}

最后一个模型是OfferCountries 和offers 关系。我们必须提供relatedKey 参数来告诉 Eloquent 在哪个字段中查找外键：

OfferCountries.php

class OfferCountries extends Model
{
    function offers()
    {
        return $this->belongsToMany(Offer::class, null, null, null, null, 'offer_id');
    }
}

https://laravel.com/docs/5.8/eloquent-relationships#many-to-many

【讨论】：

【解决方案3】：

您没有遵循标准命名约定，因此您必须明确传递那些相关的键和表名。

Offer.php

use App\OfferCategory;
use App\OfferCountries;
use App\OfferCreative;
use App\OfferTools;
use App\OfferTraffic;

class Offer extends Model {
 public function offer_countries() {
     return $this->belongsToMany(OfferCountries::class, 'offer_offer_countires', 'offer_id', 'offer_countries_id');
 }

 public function offer_categories() {
     return $this->belongsToMany(OfferCategory::class, 'offer_offer_categories', 'offer_id', 'offer_category_id');
 }

 public function offer_creatives() {
     return $this->hasMany(OfferCreative::class, 'offer_id');
 }

 public function offer_tools() {
     return $this->hasMany(OfferTools::class, 'offer_id');
 }

 public function offer_traffic() {
     return $this->hasMany(OfferTraffic::class, 'offer_id');
 }

 public function platforms() {
     return $this->hasMany(Platform::class, 'offer_id');
 }
}

OfferCountries.php

use App\Offer;

class OfferCountries extends Model {

   function offers() {
         return $this->belongsToMany(Offer::class, 'offer_offer_countires', 'offer_countries_id', 'offer_id');
    }
}

【讨论】：